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Dave001
Explorer
June 19, 2025
Solved

Struggling with STM32L432 CAN Bus communication using MCP2551

  • June 19, 2025
  • 2 replies
  • 585 views

Hi all,

I am Struggling with STM32L432 CAN Bus communication from one STM32L432 to another STM32L432 using MCP2551.

* I have checked loopback works.

*I am using HSE Clock (After soldering SB17) - 

Dave001_0-1750297415512.png

Dave001_1-1750297436889.png

 

* I have also tried putting Oscilloscope at TX pins between STM32 Transmitter and MCP2551 but signal just stays high.

* Plus, i can see that this never triggers but putting it in debug mode and putting a breakpoint in there

Dave001_2-1750297571288.png

 

I also tried following this guy: 115. STM32CubeIDE MCP2551 CAN BUS with STM32 F103C8T6 

but to no avail. 

* I also tried doing the same setup i.e. ADC on transmitter sending information to other side via CANBUS.

* I have quadrupled checked Hardware circuitry, and all seems to be right.

* CANBUS Distance is also less than a meter now with termination at both ends.

TX Code - 

Dave001_5-1750297828603.pngDave001_6-1750297837587.png

 

 

RX Code - 

Dave001_3-1750297798394.png

Dave001_4-1750297807967.png

 

 

Any help would be much appreciated.

 

Thanks

 

    This topic has been closed for replies.
    Best answer by mƎALLEm

    Hello @Dave001  and welcome to the ST community,

    First in next time please use </> button to share your code instead of sharing screen shots. Please review how to post a code.

    Second, these are a very bad bit timing parameters:

    mALLEm_0-1750327556925.png

    You need to decrease as much as possible the Prescaler and increase as much as possible BS1 and BS2 while having a simple point at around 87%;

    Refer to this article: CAN (bxCAN) bit time configuration on STM32 MCUs

    This link can help you to calculate the timings parameters. You need to select:

    mALLEm_0-1750328006080.png

    Hope that helps.

     

    2 replies

    M
    mƎALLEmAnswer
    Technical Moderator
    June 19, 2025

    Hello @Dave001  and welcome to the ST community,

    First in next time please use </> button to share your code instead of sharing screen shots. Please review how to post a code.

    Second, these are a very bad bit timing parameters:

    mALLEm_0-1750327556925.png

    You need to decrease as much as possible the Prescaler and increase as much as possible BS1 and BS2 while having a simple point at around 87%;

    Refer to this article: CAN (bxCAN) bit time configuration on STM32 MCUs

    This link can help you to calculate the timings parameters. You need to select:

    mALLEm_0-1750328006080.png

    Hope that helps.

     

      D
      Dave001Author
      Explorer
      June 19, 2025

      YOU ARE A LEGEND!!!

       

      Thank you.... i was stuck on this for so long.

        O
        Obaid_tanveer
        Graduate II
        June 19, 2025

        You should try playing with the parameters , increase the sample points , use internal/ external loop back mode and see if the RxCallback Triggers, you can refer to https://kvaser.com/support/calculators/bit-timing-calculator/ this website for the CAN bus timing parameters , works well with the ST Boards and is easy to use, You will most likely get the Communication started.

        D
        Dave001Author
        Explorer
        June 19, 2025

        Thank you for commenting, Much appreciated.

         

        Problem is resolved by mƎALLEm.

         

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